Abstract
Pistachios are high in lutein, beta-carotene, and gamma-tocopherol relative to other nuts; however, studies of the effects of pistachios on oxidative status are lacking. We conducted a randomized, crossover controlled-feeding study to evaluate 2 doses of pistachios on serum antioxidants and biomarkers of oxidative status in 28 hypercholesterolemic adults (LDL-cholesterol >or=2.86 mmol/L). Participants consumed 3 isoenergetic diets for 4 wk each after a 2-wk baseline Western diet. Experimental diets included a lower-fat control diet without pistachios (25% total fat) with 1 serving/d (i.e. 32-63 g/d; energy adjusted) of pistachios (1 PD; 10% energy from pistachios; 30% total fat) or with 2 servings/d (63-126 g/d; energy adjusted) of pistachios (2 PD; 20% energy from pistachios; 34% total fat). When participants consumed the pistachio-enriched diets, they had higher plasma lutein (P < 0.0001), alpha-carotene, and beta-carotene (P < 0.01) concentrations than after the baseline diet. After consuming the pistachio diets, participants had greater plasma lutein (P < 0.001) and gamma-tocopherol (P < 0.05; 2 PD only) relative to the lower-fat control diet. After the 2 PD diet period, participants also had lower serum oxidized-LDL concentrations than following the baseline diet period (P < 0.05). After both the 1 PD and 2 PD diet periods, they had lower serum oxidized-LDL concentrations than after the control diet period (P < 0.05). The change in oxidized-LDL from baseline correlated positively with the change in LDL-cholesterol across all treatments (r = 0.42; P < 0.005). After controlling for the change in serum LDL-cholesterol as a covariate, increases in serum lutein and gamma-tocopherol following the 2 PD period were still modestly associated with decreases in oxidized-LDL (r = -0.36, P = 0.06 and r = -0.35, P = 0.08, respectively). This suggests that a heart-healthy diet including pistachios contributes to the decrease in the serum oxidized-LDL concentration through cholesterol-lowering and may provide an added benefit as a result of the antioxidants the pistachios contain.